Ni/Fe物质的量的比对Ni-Fe催化剂表面性质和二硝基甲苯加氢活性的影响

采用Fe粉置换氯化镍溶液中的Ni²⁺制备了Ni-Fe催化剂, 并应用于催化二硝基甲苯加氢合成甲苯二胺的反应中。运用XRD、低温氮吸附-脱附、H₂-TPD、XPS和TEM等技术手段对不同Ni/Fe物质的量的比(n_Ni/n_Fe)下催化剂进行了表征。结果表明, n_Ni/n_Fe对Ni-Fe催化剂表面性质影响显著。当n_Ni/n_Fe为1:4时, Fe抑制Ni氧化的作用达到最大, Ni-Fe催化剂化学氢吸附量和活性物种Ni的分散度分别达到了0.16 mmol·g^-1和23%, 催化剂性能得到较大的提升。在优化的催化剂制备条件下, DNT(二硝基甲苯)的转化率和TDA(甲苯二胺)的选择性分别达到了~100%和99%。另外, 对Ni-Zn漆原镍(Urushibara Ni)催化剂和Ni-Fe催化剂催化DNT加氢反应进程进行了研究, 发现它们有相同的加氢中间产物, 但反应不同阶段的催化速率存在差异。

Influence of Ni/Fe Molar Ratio on Surface Properties of Ni-Fe Catalysts and Hydrogenation Performance of Dinitrotoluene

Ni-Fe catalysts were prepared via the replacement reaction of NiCl2 by Fe and used for the selective hydrogenation of dinitrotoluene (DNT) in liquid phase. The influences of Ni/Fe molar ratio (n_Ni/n_Fe) on the surface properties and catalytic performance of Ni-Fe catalysts were investigated. The characterization results from XRD, Low temperature nitrogen adsorption -desorption, H₂-TPD, XPS and TEM show that n_Ni/n_Fe has a significant effect on the surface properties of Ni-Fe catalysts. When n_Ni/n_Fe is 1:4, the effect of Fe inhibition on the oxidation of nickel is more apparent, the chemical adsorption of hydrogen is 0.16 mmol·g^-1 and the dispersion of active species Ni achieves 23%. The performance of Ni-Fe catalysts is greatly improved. Under the optimized catalysts preparation conditions, the conversion of DNT (dinitrotoluene) and the selectivity of TDA (toluenediamine) could reach~100% and 99%, respectively. In addition, Ni-Zn Urushibara nickel catalysts and Ni-Fe catalysts have~the same catalytic hydrogenation~pathway but different catalytic reaction rate in a different reaction stages.